TWI839545B - Cogset and sub-assembly for bicycle rear wheel - Google Patents

Abstract

The cogset (20) has the first n sprockets (26a, 26b, 26c), with 6 > n > 3, fixedly connected to one another so as to form a monolithic set (26), adapted for being mounted directly in shape engagement on a coupling profile (16) formed on the radially peripheral surface of a sprocket-carrying body (14) through a coupling profile (32) formed on the radially inner surface of at least the largest sprocket (26a) of the monolithic set (26).

The direct shape coupling between the largest sprocket (26a) of the monolithic set (26) and the sprocket-carrying body (14), and the fact that this direct coupling is made between the radially peripheral surface of the sprocket-carrying body (14) and the radially inner surface of the largest sprocket (26a) (or of the largest sprockets) of the monolithic set (26), makes it possible to have very high solidity and rigidity of coupling, so as to ensure the maximum precision of actuation of the gearshift that uses the subassembly.

Description

Shift plates and subassemblies for bicycle rear wheels

The present invention relates to a sprocket carrier and a subassembly for a rear wheel of a bicycle, the subassembly being formed by the sprocket carrier and a shift plate, the shift plate being coaxially mounted on the sprocket carrier by shape engagement of the shift plate on a coupling profile formed on the radial outer peripheral surface of the sprocket carrier and extending in the axial direction.

In the following, spatial indications (particularly radial, axial and circumferential) will be provided with reference to the axis of rotation of the rear wheel of the bicycle, which axis of rotation coincides with the axis of the gear chain, the axis of the sprocket carrier, the axis of the hub of the wheel and generally the axes of all elements rotating with the wheel. Furthermore, an axial direction will be indicated as being towards the outside if it is away from the longitudinal median plane of the bicycle or away from the hub of the wheel, whereas it is indicated as being towards the inside if it is towards such a median plane or towards the hub. In addition, in the radial direction, the orientation away from the rotation axis will be indicated as peripheral; conversely, the orientation toward the rotation axis will be indicated as internal.

To mount the gearshift chain on the hub of the rear wheel of a bicycle, a so-called sprocket carrier is usually used, which is made on one side to rotate as a unit with the sprocket by a form-fitting connection, and on the other side is made to rotate as a unit with the hub (however, in a unidirectional manner) by a set of ratchets or similar (usually called freewheels). In this way, the transmission chain engaged with each sprocket is able to transmit torque to the hub in the forward direction of the bicycle.

The sprocket carrier is essentially composed of a tubular body which is mechanically coupled at its radial peripheral surface to a central mounting opening made in the sprocket. The radial peripheral surface of the sprocket carrier is shaped with substantially axial ribs and grooves alternating in the circumferential direction, which are suitable for allowing coupling of the aforementioned shape. To this end, the central mounting opening of the sprocket is provided with a radially inward extension or projection (i.e. pointing towards the axis of rotation) which couples with a groove present on the sprocket carrier.

Thus, the sprockets are axially mounted on the sprocket carrier in order from the sprocket with the largest diameter, so that when the sprocket carrier is mounted on the hub of the wheel of a bicycle, the sprocket with the largest diameter is positioned toward the inside, i.e., close to the rear wheel, while the sprocket with the smallest diameter is positioned toward the outside.

In most modern bicycle derailleurs, especially for bicycles intended for competition, there is a well-known trend towards increasing the number of sprockets. When the gearbox reaches 11, 12 or even more sprockets, there may be no front derailleur; this simplifies the bicycle and makes it lighter, which is undoubtedly beneficial to the cyclist, as long as this is not accompanied by a negative impact on the availability of gear ratios.

To achieve this result, it is necessary to have small sprockets with a very small number of teeth (e.g. 10 or 9) in the derailleur. However, a reduction in the number of teeth is obviously accompanied by a reduction in the diameter, which may eventually make the diameter too small to be mounted on a normal sprocket carrier.

Thus, a gearshift chain has been realized in which the smallest sprockets are made fixedly connected to one another to form a one-piece set (also called a double, triple or quadruple, precisely because it groups two, three or four sprockets together) and the central opening for mounting on the sprocket carrier extends axially only at the largest sprocket of the set; the smallest sprockets extend more towards the axis of rotation, but do not engage directly with the sprocket carrier, since their movement can be ensured by the fact that they are fixedly connected to the largest sprocket of the set. In this way, the smallest sprocket of the set can have 10 teeth or even fewer; on the other hand, the largest sprocket of the set must have at least 11 teeth to engage with the sprocket carrier.

Therefore, there are constraints that reflect the practical possibilities of manufacturing. For example, in the case of a double chain (one-piece set of two chainrings), it is necessary to have a first chainring with 10 teeth (and not 9 or less), or to accept a tooth difference between the first and second chainrings equal to or greater than 2; however, this condition does not suit cyclists who are usually accustomed to a difference of a single tooth between adjacent chainrings at a minimum.

In some cases, in an attempt to manage the constraints imposed by specific conditions, shaped couplings with projections or teeth extending in the axial direction between the largest sprocket of the one-piece set and the sprocket carrier are used, or couplings by threaded portions that engage differently between the one-piece set and the sprocket carrier. However, these couplings do not ensure the same robustness as shaped couplings with grooved profiles.

Therefore, more flexibility is needed in choosing the number of teeth on the smallest sprocket of the derailleur.

Thus, the invention in its first aspect relates to a gearshift disc according to claim 1; in its second aspect, the invention relates to a subassembly according to claim 12. Preferred features of the gearshift disc and the subassembly are provided in the dependent claims.

More particularly, according to a first aspect of the present invention, the shifting disc includes a plurality of axially adjacent sprockets between a first sprocket having the smallest number of teeth and a last sprocket having the largest number of teeth, wherein the first n sprockets (where 6≧n≧3) are fixedly connected to each other to form an integral kit, wherein the integral kit is adapted to be directly form-engaged on a coupling profile formed on a radially outer peripheral surface of a sprocket carrier through a coupling profile formed on a radially inner surface of at least the largest sprocket of the integral kit.

Having at least three sprockets grouped as an integral set makes it possible to have a sprocket with 11 teeth adapted to engage directly on the sprocket carrier and two or more smaller sprockets suspended; thus, the first sprocket can have as few as 9 teeth (or less) without having to accept a difference of more than 1 between the number of teeth of the adjacent smallest sprockets. Furthermore, the fact that a direct positive connection is provided between the largest sprocket of the one-piece set and the sprocket carrier, and that this direct connection is made between the radially outer peripheral surface of the sprocket carrier and the radially inner surface of the largest sprocket (or largest sprocket) of the one-piece set, enables very high robustness and rigidity, thus ensuring maximum actuation precision for a shifter using a subassembly, which is comparable to the precision of a shifter with the sprockets of the shifting discs mounted individually and directly so as to rotate as a unit on the sprocket carrier.

Preferably, the first sprocket has 10, 9 or even 8 teeth. This enables very long gear ratios of the transmission.

Preferably, the number n of sprockets of the one-piece set is equal to 3, 4, 5 or even 6. The greater this number n, the greater the flexibility in choosing the number of teeth per sprocket and therefore the gear ratio.

In the case of a one-piece kit having five sprockets, the connection profile between the one-piece kit and the sprocket carrier is preferably formed on the radially inner surfaces of the two largest sprockets of the one-piece kit.

In the case of a one-piece kit having six sprockets, the connection profile between the one-piece kit and the sprocket carrier is preferably formed on the radially inner surfaces of the three largest sprockets of the one-piece kit.

These features make it possible to maintain the robustness and rigidity of the connection between the sprockets of the one-piece set and the sprocket carrier even in the case of a relatively high number n of sprockets of the one-piece set.

Preferably, the gearshift plate comprises 12, 13 or even 14 sprockets. The invention is indeed particularly noteworthy when the number of sprockets is greater than 11.

According to a second aspect of the present invention, a subassembly includes a sprocket carrier and a shift plate coaxially mounted on the sprocket carrier, wherein the shift plate includes a plurality of axially adjacent sprockets between a first sprocket having a minimum number of teeth and a last sprocket having a maximum number of teeth, wherein the first n sprockets (where 6≧n≧3) are fixedly connected to each other to form an integrated kit, and wherein the integrated kit is directly shape-engaged on a coupling profile formed on a radially outer peripheral surface of the sprocket carrier through a coupling profile formed on a radially inner surface of at least the largest sprocket of the integrated kit.

Preferably, the one-piece kit comprises an axially adjacent surface which is in adjacent engagement with a corresponding outer axially adjacent surface of the sprocket carrier. This allows for a precise and stable axial positioning of the one-piece kit relative to the sprocket carrier.

Preferably, the sprocket carrier includes a radially inner threaded portion.

Preferably, the subassembly further comprises a ring nut having a threaded portion which is driven into the radially inner threaded portion of the sprocket carrier.

The attachment via the ring nut ensures stable and precise axial positioning of the entire shifting plate on the sprocket carrier.

1: Wheel hub assembly

2: Subcomponents

10: Wheel hub

11: Sales

12: Bearings

14: Sprocket carrier

15: Bearings

16: Groove

17: Axial adjacent surface

18: End stop

20: Gearbox

21: All-in-one kit

21a: Chain wheel

21b: Sprocket

21c: Chain wheel

22: All-in-one kit

22a: Chain wheel

22b: Chain wheel

22c: Chain wheel

23: Sprocket

24: Sprocket

25: Sprocket

26: All-in-one kit

26a: Chain wheel

26b: sprocket

26c: sprocket

27: Adjacent surface

28: Ring nut

29: External thread part

30: Radial inner thread part

31: flange

32: protrusion

126: All-in-one kit

126a: Chain wheel

126b: sprocket

126c: sprocket

126d: sprocket

132: radial inward protrusion

Other features and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the accompanying drawings. In such drawings: FIG. 1 is a perspective view of a hub of a bicycle rear wheel with a subassembly and a gear shifter according to the present invention; FIG. 2 is an axial cross-sectional view of the hub of FIG. 1; FIG. 3 is an enlarged cross-sectional view of a portion of the hub of FIG. 2; FIG. 4 is a perspective view of the subassembly of FIG. 1 with parts removed to better illustrate the one-piece kit of the sprocket carrier and the smallest sprocket; FIG. 5 is a perspective view of only the one-piece kit shown in FIG. 4; FIG. 6 and FIG. 7 are perspective views of variants of the one-piece kit from different angles; FIG. 8 is a cross-sectional view of the one-piece kit of FIG. 6 and FIG. 7.

FIG. 1 illustrates a hub 10 of a hub assembly 1 (not shown) for a rear wheel of a bicycle, which hub 10 is coaxially mounted on a pin 11 by means of a bearing 12; the hub 10 is thus free to rotate on the pin 11, which is intended to be fixedly mounted on the frame of the bicycle.

The wheel hub 10 is coupled to the sprocket carrier 14 via a flywheel mechanism (not highlighted) which ensures that the wheel hub 10 is set to rotate only in the direction determining the forward movement of the bicycle and not in the opposite direction via the sprocket carrier 14. The sprocket carrier 14 has an approximately tubular shape and is freely mounted on the pin 11 by means of a bearing 15. The sprocket carrier 14 is provided with a coupling profile formed by grooves 16 arranged in the axial direction on its radial outer peripheral surface. Furthermore, the sprocket carrier 14 is provided with an end stop 18 near its axial inner end, which is in the form of teeth protruding from the sprocket carrier 14 in the radial direction; alternatively, a flange extending along the entire circumference of the sprocket carrier 14 can be provided as the end stop 18 instead of the teeth.

The sprocket carrier 14 has a substantially annular axial abutment surface 17 at its outer axial end.

The shifting plate 20 is mounted on the sprocket carrier 14 to form the subassembly 2. The shifting plate 20 shown includes 12 sprockets arranged in order from the largest to the smallest as follows: the three largest sprockets 21a, 21b, 21c are made to be fixedly connected to each other to form a one-piece set (or a triple piece) 21; the next three sprockets 22a, 22b, 22c are made to be fixedly connected to each other to form a one-piece set (or a triple piece) 22; the next three sprockets 23, 24, 25 are independent of each other; and the three smallest sprockets 26a, 26b, 26c are made to be fixedly connected to each other to form a one-piece set (or a triple piece) 26. These elements are mounted peripherally on the sprocket carrier 14, wherein the one-piece set 21 is axially arranged at the end stop 18, the one-piece set 22 is axially arranged at the one-piece set 21, the sprocket 23 is axially arranged at the one-piece set 22, the sprocket 24 is axially arranged at the sprocket 23, the sprocket 25 is axially arranged at the sprocket 24, and the one-piece set 26 is axially arranged at the sprocket 25.

The one-piece sets 21, 22 and the sprockets 23-25 are slotted into the sprocket carrier 14 and are constrained in rotation relative to the sprocket carrier 14, but are substantially free in the axial direction; the constraint in rotation is ensured in a conventional manner per se by the grooves 16 engaging corresponding projections (not visible in the accompanying drawings) on the radially inner surfaces of the one-piece sets 21, 22 and the sprockets 23-25.

As mentioned above, in the subassembly 2 formed by the sprocket carrier 14 and the shift plate 20, 12 sprockets are installed individually or grouped into a one-piece set. In particular, there is a very small sprocket (i.e., sprocket 26c) whose number of teeth is too small to be installed on the sprocket carrier 14 without grouping it into a one-piece set 26. In fact, if this small sprocket is single, it will be too small to be slotted into the sprocket carrier 14; on the other hand, the one-piece set 26 can have an inner axial portion at the sprocket 26a (with 12 teeth) that is sized to be able to engage on the sprocket carrier 14.

The one-piece set 26 (particularly visible in FIGS. 4 to 8 ) comprises, at the largest sprocket 26 a, a series of protrusions 32 facing radially inwards, which overall constitute an inner shaped coupling profile formed on the radially inner side surface of the sprocket 26 a. This coupling profile formed by the protrusions 32 has a shape that corresponds to the shape of the coupling profile formed by the grooves 16 on the radially outer peripheral surface of the sprocket carrier 14. Thus, in installation, the one-piece set 26 is partially slotted onto the sprocket carrier 14, wherein the protrusions 32 engage in the grooves 16, while the smallest sprockets 26 b and 26 c of the one-piece set 26 remain axially suspended. This arrangement on the radially peripheral surface of the sprocket carrier 14 ensures that the entire one-piece set 26 (and therefore all its sprockets 26a, 26b and 26c) are made to rotate as a unit with the sprocket carrier 14 in a stable and secure manner; thus, any uncertainty in the connection (i.e. any possibility of angular micro-displacements of the one-piece set 26 relative to the sprocket carrier 14) that would make the operation of the derailleur using the subassembly 2 inaccurate is excluded.

The one-piece set 26 has a substantially annular axial abutment surface 27 at the inner shape coupling contour formed by the protrusion 32. The abutment surface 27 abuts against the axial abutment surface 17 of the corresponding sprocket carrier and thus serves as a reference for the axial positioning of the one-piece set 26 to prevent its axial sliding.

Towards the inside in the axial direction (i.e. towards the wheel hub 10), the entire shift plate 20 (i.e. the one-piece sets 21, 22 and 26 and the sprockets 23-25) is held by the end stop 18; towards the outside in the axial direction, the shift plate 20 is held by the ring nut 28, plugged onto the pin 11 and screwed onto the sprocket carrier 14 by means of the outer thread 29 of the ring nut 28 and the radial inner thread 30 of the sprocket carrier 14. The ring nut 28 has a flange 31 which abuts axially against the outer surface of the one-piece set 26. The clamping of the ring nut 28 ensures that the entire shift plate 20 is locked to the sprocket carrier 14 by means of the axial pressure exerted on the shift plate 20 by the flange 31 and the end stop 18.

In use, due to the engagement of the protrusion 32 in the groove 16, the connection of the one-piece assembly 26 to the sprocket carrier 14 is particularly strong and thus ensures high-precision actuation.

As mentioned above, the one-piece kit 26 shown in Figures 1 to 5 includes the three smallest sprockets 26a, 26b and 26c of the gear plate 20. However, according to the present invention, the number of sprockets of the one-piece kit can also be higher, up to 6. For example, Figures 6 to 8 illustrate a one-piece kit 126 (quadruple), which groups together four smallest sprockets 126a, 126b, 126c and 126d having 12, 11, 10 and 9 teeth, respectively.

In the one-piece set 126, radially inward projections 132 are formed at the two largest sprockets 126a and 126b. Generally, when the number of smallest sprockets grouped as a one-piece set increases, it is possible to ensure that radially inward projections are formed at more than one sprocket in order to increase the robustness of the connection. If the number of smallest sprockets grouped as a one-piece set becomes particularly high (e.g. 5 or 6), it is undoubtedly preferred to form radially inward projections at more than one sprocket (e.g. 2 or 3) in order to reduce the axial extension of the suspended part of the one-piece set, thereby increasing the torsional rigidity of the one-piece set itself; this arrangement also facilitates the actuation accuracy of the derailleur using this subassembly.

14: Sprocket carrier

16: Groove

18: End stop

26: All-in-one kit

26a: Chain wheel

26b: sprocket

26c: sprocket

32: protrusion

Claims (15)

A gear shifting disc for a rear wheel of a bicycle, the gear shifting disc comprising a plurality of adjacent sprockets (21a, 21b, 21c, 22a, 22b, 22c, 23, 24, 25, 26a, 26b, 26c; 126a, 126b, 126c, 126d) adapted to be coaxially mounted on a sprocket carrier (14), the number of the plurality of adjacent sprockets being between 12 and 14 sprockets, a first sprocket (26c; 126d) having the smallest number of teeth, and a last sprocket (21a) having the largest number of teeth , wherein n sprockets (26c, 26b, 26a; 126d, 126c, 126b, 126a) from the plurality of sprockets are fixedly connected together in an integrated kit, wherein the range of n is 6≧n≧3, and the integrated kit (26; 126) is suitable for being directly connected to a connecting profile formed on the radial outer peripheral surface of the sprocket carrier (14) through a connecting profile formed on the radial inner side surface of at least the largest sprocket (26a; 126a, 126b) of the integrated kit (26). A shifting disc as claimed in claim 1, wherein the first sprocket (26c) in the one-piece kit has 10 teeth. A shift plate as claimed in claim 1, wherein the first sprocket (126d) in the one-piece kit has 9 teeth. A shifting disc as claimed in claim 1, wherein the first sprocket in the one-piece kit has 8 teeth. A speed change plate as described in claim 1, wherein n=3. A speed change plate as described in claim 1, wherein n=4. A gear shifting disc as claimed in claim 1, wherein n=5, and the connection profile between the one-piece kit (126) and the sprocket carrier (14) is formed on the radial inner surface of the two largest sprockets (126a, 126b) of the one-piece kit. A gear shifting disc as described in claim 1, wherein n=6, and the connection profile between the one-piece kit and the sprocket carrier is formed on the radial inner surface of the two largest sprockets of the one-piece kit. A subassembly for a rear wheel of a bicycle, the subassembly comprising a sprocket carrier (14) and a shift plate (20) coaxially mounted on the sprocket carrier (14), wherein the shift plate (20) comprises a plurality of 12 to 14 axially adjacent sprockets (21a, 21b, 21c, 22a, 22b, 22c, 23, 24, 25, 26a, 26b, 26c; 126a, 126b, 126c, 126d) between a first sprocket (26c; 126d) having the smallest number of teeth and a last sprocket (21a) having the largest number of teeth, wherein the sprockets are coaxially mounted on the sprocket carrier (14). Mounted on a sprocket carrier, wherein n sprockets (26c, 26b, 26a; 126d, 126c, 126b, 126a) of the plurality of axially adjacent sprockets are fixedly connected (26; 126) in an integrated kit, wherein the range of n is 6≧n≧3, and wherein the integrated kit (26; 126) is directly connected in shape to a connecting profile formed on the radial inner surface of at least the largest sprocket (26a; 126a, 126b) of the integrated kit (26; 126) through a connecting profile formed on the radial inner surface of at least the largest sprocket (26a; 126a, 126b) of the integrated kit (26; 126) on the radial outer peripheral surface of the sprocket carrier (14). A subassembly as claimed in claim 9, wherein the one-piece kit (26; 126) includes an axially adjacent surface (27) which is in abutting engagement with a corresponding outer axially adjacent surface (17) of the sprocket carrier (14). A subassembly as described in claim 10, wherein the sprocket carrier (14) includes a radial inner threaded portion (30). The subassembly as described in claim 9 further includes a ring nut (28) having a threaded portion (29) which is inserted into the radial inner threaded portion (30) of the sprocket carrier (14). The subassembly as described in claim 10 further includes: a ring nut (28), the ring nut (28) having a threaded portion (29), the threaded portion (29) being inserted into the radial inner threaded portion (30) of the sprocket carrier (14). The subassembly as described in claim 11 further includes: a ring nut (28), the ring nut (28) having a threaded portion (29), the threaded portion (29) being inserted into the radial inner threaded portion (30) of the sprocket carrier (14). A gear shifter for a rear wheel of a bicycle, the gear shifter comprising: at least 12 and no more than 14 sprockets adapted to be coaxially mounted on a sprocket carrier, wherein a first sprocket has the smallest number of teeth and a last sprocket has the largest number of teeth, and the n sprockets are fixed together in an integral kit including the first sprocket, wherein n is 6

n

3, and the one-piece kit is suitable for directly engaging with a coupling profile formed on a radial outer peripheral surface of a sprocket carrier through a coupling profile formed on a radial inner side surface of at least one largest sprocket of the one-piece kit.